Your Eyes and VDU's

There is some disagreement about whether visual display unites, such as computer monitors, can cause permanent damage to the eyes, but we do know that environmental factors affect visual comfort and performance.

The advice given below is intended to help create a more pleasant and less fatiguing working environment.

The incidence of ocular discomfort amongst VDU users is about double that found in the rest of the working population. Therefore, people intending to work with VDU's on a regular basis should have an initial eye examination. This enables the Optometrist to assess whether there is any likelihood of problems arising and to establish a basis for future comparisons.

Eyestrain

Visual comfort and visual efficiency are related but are not the same. It is possible to have no visual discomfort and yet not see clearly, and alternatively to see very well whilst suffering from visual fatigue.

If the eyes are having to take in a large amount of detail over a long period of time, the likelihood of eyestrain increases.

Eyestrain is a term used to describe a wide range of symptoms, including tiredness, irritation, soreness and photophobia (sensitivity to light).

VDU and Microfiche users are more prone to eyestrain than the average worker. The most common causes are a fault in the focusing of the eye, poor eye co-ordination, incorrect positioning of the equipment and documents, inappropriate lighting, poorly designed work areas and lack of adequate maintenance., all of which can be corrected by attention to the work environment and regular visits to the Optometrist.

Development of the Eye

As we grow, our eyes should develop so that we can see clearly at a variety of distances, without any focusing adjustment. If the eyes stop growing before reaching their optimum size, they become long sighted (hypermetropic). This may result in difficulty when focusing on things close to and often makes reading a problem. In about 30% of people, the eyes become too long, resulting in short sight (myopia). This means that near objects can be seen clearly, but distance vision is blurred. Myopia tends to increase rapidly during adolescence, but can also develop in later years.

Regular examinations measure the rate at which the eyes are changing. Frequently a tendency towards myopia can be detected in advance and advice is then given on how to minimize the condition. If there is any doubt about visual efficiency, professional advice should be obtained.

Young people with normal sight have a wide range of clear vision at all distances. This is due to the powerful focusing system of the eyes. Gradually, however, the nearest point on which we can focus begins to recede and close work difficulties (presbyopia) often start to occur around the age of forty.

Eyes cannot focus on close work for long periods without fatigue, and this gets worse as we get older. Surveys indicate, especially amongst non-spectacle wearers, that a considerable period may elapse between noticing a reduction in performance and seeking professional help. Therefore a visual examination at least every two years is advisable.

The Use of Spectacles

To enable older users to see both the display and the documents, spectacles specifically prescribed for use with the VDU may be necessary, possibly in the form of bifocal, trifocal or progressive or multifocal lenses. It is sometimes stated that bifocals are unsuitable for VDU use. This misunderstanding stems from the use of lenses designed for long and close distances instead of for the appropriate working range. Reading glasses and the use of document holders are then advocated as a "poor" substitute.

Straight line bifocals tend to be superior to those with "round" or "crescent" shapes, as they give a greater area of useful lens and minimize head and eye movements. They also reduce the "jump" of displacement of objects between the different sections of the lens.

Astigmatism

Astigmatism means that the "front window" of the eye requiring correction tends to be slightly irregular (egg shaped) instead of spherical (ball shaped). THis defect is a particularly significant cause of symptoms associated with detailed work and needs to be corrected by spectacles for VDU or Microfiche users.

Contact Lenses

Contact lenses are very suitable with VDU's as they give less distortion and reflection than spectacles. However, when first used with VDU's, problems may arise if the lenses start to dry. This problem usually disappears once the wearer has got used to the lenses. It is important to keep contact lenses clean and free from scratches to achieve best possible vision in all circumstances.

Contact lenses correct distance vision and so older users of VDU's may also need additional reading glasses.

Eye Co-ordination

Movements of each eye are controlled by means of six separate muscles. The slightest malfunction of any of these muscles or their nerve supply can lead to poor ocular co-ordination, with consequent feelings of fatigue, ocular discomfort, headaches or even blurred or double vision, at one or all of the working distances. Indeed such malfunctions may cause more trouble amongst VDU operators than any other defects of vision. The detection of poor eye co-ordination is a simple matter for the optometrist during a routine eye examination.

Eye Exercises

If the eyes do not work as a well matched pair, eye exercises (orthoptics) can sometimes solve the problem, although it is sometimes necessary to wear spectacles as well. During treatment, the patient may have to spend a short time each day practicing the exercises.

Colour Deficiency

This condition should not normally stop anyone from working with VDU's, since the screen characters invariably contrast with the display background. Poor colour recognition affects about one in eight men and one in sixty-four women. These operators can distinguish between different brightness levels rather than differences in hue. With multicolour displays, a practical check on the colours to be used provides an additional safeguard.

Vision Screening

Whilst an eye examination for VDU use may take 20-30 minutes, vision screening records certain useful information in a fraction of that time. It is now, however, a substitute for a full eye examination. Pathological conditions may be overlooked, there is little or no opportunity for assessing history and symptoms, and comprehensive advice is absent. Screening is only useful in ensuring that initial standards are met.

Medical History

Where there is a history of headaches, or marked discomfort from flicker, television or fluorescent lighting, professional advice should be obtained before commencing VDU work. Migraine sufferers in particular should have a thorough eye examination.

Positioning the Equipment

There should be sufficient space behind the VDU for the operator to be able to look past the screen in to an area which is free of movement and visually pleasing as this will relax the eyes.

Ventilation, temperature and humidity are important, especially as the blink rate may be reduced with concentration. Drying of the eyes through draughts, excess heat or lack of moisture in the air causes rapid discomfort and tiredness, particularly with contact lens wearers.

Lighting

Many of the problems associated with VDU work are a result of glare caused either by reflections on the screen, or by excessive contrasts between the text, screen and surroundings.

Operators should not have unshielded windows in front or behind them. Any other window reflected in the screen face should be fitted with curtains or blinds. Vertically louvred blinds with a matt finish offer an effective solution. Desk surfaces should not be reflective and should preferably have a medium colour finish.

Screen and Filters

A wide variety of screens and VDU glasses are marketed to reduce glare and reflection. Those items may help with a specific individual case but the necessary filters will have been incorporated into the display if the VDU is well designed. Any additions may ease one problem, but create another.

Document Holders

It is advisable to have a document holder available. The holder should be easily movable, adjustable for height and able to hold its contents securely in any position, from horizontal to vertical. Where the document detail is small, the holder should be positioned closer than the screen distance.

Psychological Considerations

Some tasks are fatiguing, either by being physically or mentally demanding or by being monotonous. Complaints of eyestrain can be caused by psychological facts such as stress, poor motivation and lack of interest.

Where VDU's are used for prolonged periods and especially trainees, provision should be made to vary the operator's visual tasks for short periods every hour or so, as this will help to reduce fatigue.

During the training, the mental concentration and unfamiliar visual task can be expected to casue eyestrain. In many cases the discomfort is tempory.